1. Field of the Invention
The present invention relates to a catheter comprising an elongated tube having a first channel for the guiding of a radioactive element and a second channel for the passage of a guide wire for the catheter, the elongated tube being provided with temporarily activatable centering means on its outer circumference near its distal end.
2. Description of the Related Art
Such a catheter known from EP-A-0 688 580 is intended for use after a recanalization treatment in which a substantially occluded blood vessel (for example as a result of the deposition of so-called plaque within the lumen of the blood vessel) is stretched by means of an expandable element such as a fluid-inflatable recanalization balloon, fastened at the distal end of an elongated catheter tube in order to permit the blood to flow unimpeded through the stretched blood vessel.
If is frequently found after a relatively short period of time that a new recanalization treatment is necessary because a constriction is again forming in the blood vessel or has already formed. The constriction may be a consequence of tissue developing at the stretched place (known as neointima proliferation), probably due to the fact that the wall of the blood vessel is damaged by the stretching. This formation of tissue can be prevented to a large extent, or at least reduced, if, during or shortly after the recanalization treatment, the blood-vessel tissue in question is irradiated with ionizing radiation, in particular xcex2 and/or xcex3 radiation.
For such a treatment, the catheter known from EP-A-0 668 580 can be used. The intensity of radiation of the radioactive element introduced decreases greatly with the distance. In order not to permit the radiation dose to be too great (damaging of vessel wall) or too low (not the intended reduction of tissue developing at the stretched place), it is important to center the radioactive element accurately in the blood vessel. This is done in the known catheter by centering means in the form of an inflatable balloon which is subdivided by constriction means into a plurality of balloon parts. The constriction means are so dimensioned that the different balloon parts communicate with each other.
Upon such a treatment, therefore, the recanalization catheter must first of all be brought to the desired place and after the carrying out of the recanalization treatment, be removed and replaced by the catheter for the guiding of the radioactive element, in which connection, of course, great care must be paid to the fact that the radioactive element can be placed precisely at the place of the earlier recanalization treatment. All in all a cumbersome and timeconsuming method which must be carried out extremely cautiously, while, also from the standpoint of the patient who must undergo the treatment, it is preferable for it to be carried out as rapidly and efficiently as possible.
The object of the present invention thus is also the provision of such an instrument that the treatment can be carried out in a short time effectively and reliably with as few manipulations as possible.
This is achieved, in accordance with the present invention, by a catheter of the type described above in the manner that the centering means are surrounded by a recanalization balloon which is inflatable by a fluid introduced via a third channel so as to form an elongated body and in the manner that the centering means are activatable within the recanalization balloon. By these measures, the recanalization treatment and the irradiation treatment of the stretched region of the blood vessel can be carried out with one and the same catheter, in other words rapidly and without loss or time, since a catheter removal action and introduction action are avoided, which also is particularly valued by the patient. Furthermore, the fact that it is not necessary to change the catheter has the particular additional advantage that the centering means are automatically located at the precisely desired place so that, in addition, there is also obtained a guarantee that the radiation will always be carried out at the correct place as well as in the correct manner.
The activating of the centering means can in this connection be carried out both simultaneously with and by the inflating of the recanalization balloon as well as independently thereof, in particular after the carrying out of the recanalization treatment.
The activating of the centering means simultaneously with the inflation of the recanalization balloon can take place automatically if, in accordance with another embodiment of the invention, the centering means are connected, on the one hand, to the recanalization balloon and, on the other hand, to the tube, all in such a manner that the tube is centered in the recanalization balloon upon the inflation thereof. The centering means can, in this connection, consist, for instance, of a number of annular parts of thin plastic material which, for the introduction of the catheter, can be laid compactly around the tube together with the recanalization balloon around the tube, and by the inflation of the recanalization balloon, come into a position extending transversely on the tube in order thus to center the tube with respect to the recanalization balloon. Furthermore, the centering means can have wire-shaped parts which, in the inflated condition of the recanalization balloon, extend radially with respect to the tube.
In accordance with another embodiment of the invention, it is also preferable for the centering means to comprise inflatable balloon means which are inflatable by fluid introduced via the third channel, the balloon means comprising a plurality of balloons which center the part of the first channel protruding between the balloons with respect to the recanalization balloon.
If preference is given to the centering means being activatable independently of the recanalization balloon, for instance after the recanalization treatment has been completed, then, in accordance with a further embodiment of the invention, it is preferred that the centering means comprise inflatable balloon means which are inflatable by fluid introduced via at least a fourth channel arranged in the tube, in which connection the balloon means comprise a number of balloons which center the part of the first channel extending between the balloons with respect to the outer circumference of the recanalization balloon. The centering balloons may consist of a plurality of balloons arranged one behind the other along the tube or of a plurality of elongated balloons which lie radially alongside of each other around the tube.
The use of the same catheter for both the recanalization treatment and the irradiation treatment results in a longer continuous dwell time of the catheter at the place of treatment than in the case of two successively introduced catheters. In this connection, it is preferred in accordance with a further embodiment of the invention that a further channel be present which extends from a distal place past the recanalization balloon and the centering means to past the proximal end of the recanalization balloon and the centering means and is provided on opposite sides of the recanalization balloon and the centering means with at least one communicating opening with the surroundings. By these measures, the flow of the blood through the treated blood vessel can remain undisturbed to a far-reaching extent, which makes special measures with regard to this generally unnecessary. This effect can be realized in particularly advantageous manner if, in accordance with another preferred embodiment of the invention, the further channel coincides with the second channel, in which case the guide wire can be pulled further back from the distal end of a second channel than the proximal connecting opening or openings. Therefore, use is made in advantageous manner of the existing channel for the guide wire, as is directly possible since the guide wire, after bringing the catheter to its place, has no further active function to perform and can be withdrawn without problems into a waiting state.